JPH1082863A - High resolution radiation imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high resolution radiation imaging device for medical or industrial use. SOLUTION: This device has at least one ionized particle detecting device 1, and the ionized particle detecting device 1 has at least one gas chamber 10 with an aperture for a side face or front face inlet where irradiating beams enter. First, second and third plate electrodes 11, 13, 14 are arranged parallel with one another in order to form a conversion space 12 and an amplification space 15. It is so constituted that a space between the second and third electrodes 13, 14 is less than 200μm and that the amplitude ratio of the electric field created between the second and third electrodes 13, 14 and between the first and second electrodes 11, 13 is larger than 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-resolution radiation imaging apparatus.

[0002]

2. Description of the Related Art Generally, current radiation imaging apparatuses have two major problems. The first is to increase the resolution of imaging, and the second is to reduce the amount of radiation given to the inspection object, and in particular, to reduce the time for exposing the inspection object to ionizing radiation.

[0003] For the purpose of increasing the resolution of imaging, it is considered that the most relevant factors are the fineness of the degree of detection of ionizing radiation irradiating the inspection object and the physical pattern obtained by this detection process. Spatial sophistication and, finally, the geometrical detail of the detector components that display these physical patterns.

Very high resolution detector components, and
The use of very small and high-amplification equipment allows the possibility of a plurality of such detection devices to be spread as appropriate for a particular field of observation. As a result, the irradiation time required for observation in this specific observation field can be reduced to the value required for observation in the elementary field according to the accuracy of the detection device parts, and therefore, the radiation dose to the inspection object is significantly reduced. Can be.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high resolution radiation imaging apparatus which satisfies the above restrictions.

Another object of the present invention is to provide an image processing apparatus having an image resolution of 100.
Still another object of the present invention is to provide a radiation imaging apparatus capable of reducing the exposure time of an inspection object to 1/10 as compared with the prior art equipment. is there.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-resolution radiation imaging apparatus using ionizing radiation, which comprises an ionizing radiation source for emitting divergent ionizing radiation, and a flat-plate radiation beam. And a detector for detecting a light beam carried through an inspection object irradiated with the flat irradiation beam, and a long axis gap forming a stop capable of emitting the flat irradiation beam.

[0008] It should be noted that the detector comprises at least one ionized particle detector, which has at least one gas chamber with an entrance window for the irradiation beam. This gas chamber is the first,
Including second and third plate electrodes, each electrode is arranged parallel to each other to form a space for converting the irradiation beam into electrons and a space for amplifying these electrons. The entrance window is arranged flush with the conversion space to ensure that the illumination beam enters the conversion space, and the amplification length of the amplification space is the distance separating the second and third electrodes and 20.
Made less than 0 μm. The detection device further comprises a bias circuit, which causes the first electrode to rise to a first potential, the second electrode to rise to a second potential higher than the first potential, and the third electrode to rise. It can be raised to a third potential higher than the second potential. The second electrode is perforated to form a cathode, capable of sending electrons generated in the conversion space towards the amplification space, and the third electrode is constituted by a plurality of insulated element anodes. To form an anode. The potential applied to the first, second and third electrodes is
A first electric field and a second electric field substantially parallel thereto are generated in the conversion space and the amplification space. In each of these electric fields, electrons are reliably multiplied by the avalanche phenomenon limited to the amplification length in the amplification space, and multiplied electrons are reliably generated near the third electrode forming the anode. As shown in FIG.

A circuit for detecting and measuring the multiplied electrons is coupled to the element anode forming the anode.

The high-resolution radiation imaging apparatus is applicable to both industrial radiation imaging techniques, particularly in the fields of crystallography and material strength, and medical radiation imaging techniques.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood with reference to the following description and drawings.

1 and 2 are longitudinal sectional views of a high-resolution radiation imaging apparatus to which the present invention is applied.

FIGS. 3 and 4 are cross-sectional views taken along the line AA of FIG. 1 for first and second different embodiments of the high-resolution radiation imaging apparatus to which the present invention is applied.

FIG. 5 shows details of an embodiment of a specific detection circuit used by the high-resolution radiation imaging apparatus of the present invention.

FIG. 6 shows a detail of an advantageous embodiment of the grid forming the cathode of the detection device according to the subject of the invention.

FIGS. 7 and 8 illustrate a useful embodiment of the high resolution radiation imaging apparatus of the present invention, wherein a multi-channel structure is located within the ionizing radiation conversion space of the detector used by the apparatus. A detailed embodiment of this multi-channel structure will be shown.

FIGS. 9 to 12 show different embodiments of the high-resolution radiation imaging apparatus according to the present invention, in which a capacitive coupling circuit is used to reliably detect electrons generated by ionizing radiation.

FIGS. 13 and 14 show another embodiment of the high-resolution radiation imaging apparatus which is the subject of the present invention, and detects electrons generated by ionizing radiation by causing an optical avalanche phenomenon. I have.

FIG. 15 shows a high-resolution radiation imaging apparatus using β-ray imaging, which is the subject of the present invention.

FIGS. 16 and 17 show a high-resolution radiation imaging apparatus which is the subject of the present invention. In this apparatus, a three-dimensional analysis of an inspection object given to an irradiation beam having a predetermined solid angle is performed. Are arranged in a superimposed manner so that

A high-resolution radiation imaging apparatus using ionizing radiation according to the present invention will be described in more detail with reference to FIGS.

FIG. 1 is a cross-sectional view taken along a plane of longitudinal symmetry of the apparatus.
Is the side of the paper on which

As seen in the figure, the apparatus of the present invention comprises an ionizing radiation source labeled S for emitting divergent ionizing radiation and a long axis labeled F for forming an aperture and delivering an irradiation beam. Has gaps. In the conventional method, this irradiation beam is a flat beam of X-rays or γ-rays and is substantially distributed in a plane including the long axis gap F, that is, a plane perpendicular to the paper surface of FIG. The irradiation beam can illuminate the inspection object SU, and after being selectively absorbed by the concentration band of the inspection object SU, enters the detection device indicated by reference numeral 1 in FIG.

According to a particularly advantageous feature of the device which is the subject of the present invention, the detection device 1 comprises at least one ionized particle detection device, which is a gas chamber with a window for the entrance of the irradiation beam. With 10.

The gas chamber 10 is a conventional chamber having an inlet window F for a flat irradiation beam and a filling gas inlet part. This gas inlet part is omitted for simplification of the drawing. Introducing gas into the gas chamber in the conventional method
Based on the operation state of the radiation imaging apparatus is a subject of the present invention, a state slightly pressurized to the atmospheric pressure, or conversely,
The operation is performed at a relatively high pressure or a very low pressure close to several Torr.

As can further be seen in FIGS.
Has a first electrode 11, a second electrode 13, and a third electrode 14, these electrodes being the conversion space 12 for converting the irradiation beam into electrons and the increase of these electrons. In order to form an amplification space of reference numeral 15 for performing amplification by doubling, they are placed in a plate shape and parallel to each other.

In the embodiment of FIG. 1, the entrance window Fe is located at the same level as the conversion space 12, and the irradiation beam is parallel to the first electrode 11 and the second electrode 13,
I make sure to put it inside.

In the case of the embodiment shown in FIG. 1, since the irradiation beam is made incident on the cathode 13 and the anode 14 in parallel, the entrance window F
e is thus positioned transversely to the gas chamber 10.

Conversely, in the embodiment shown in FIG. 2, the entrance window Fe is arranged on the gas chamber surface to face the second electrode 13 so that the irradiation beam can enter the electrode from the front. .

A source S, for example, a gap F made of a lead film, a frame B
The assembly formed by the detection device 1 integrated with the above can be translated and rotated if necessary in order to properly and reliably analyze the inspection object SU. Since the required parts for making this embodiment are known to those skilled in the art, no specific structural disclosure of this assembly will be given. Further, the source S and the detection device 1
Can be fixed, and the inspection object SU can move within an appropriate range.

According to a particularly advantageous feature of the device of the invention,
The multiplication length of the amplification space 15 is less than 200 μm at the interval D between the second electrode 13 and the third electrode 14. .

According to another particularly salient feature of the device according to the invention, the first electrode 11 is raised to a first potential and the second electrode 13
Is raised to a second potential higher than the first potential, and the third electrode 14
Is increased to a third potential higher than the second potential.

As shown in FIG. 1, the bias circuit includes a reference voltage V1 having a positive electrode connected to the reference voltage VREF and the third electrode 14, and a negative electrode connected to the second electrode 13.
3 DC power supplies. The bias circuit further includes a reference V1 having a positive electrode connected to the negative electrode of the power supply V13 and a negative electrode connected to the first electrode 11.
It has one other power supply.

Thus, it can be seen that the second electrode 13 forms a cathode, while the third electrode 14 forms an anode.

The distance X between the first electrode 12 and the second electrode 13 is
It is much larger than the distance D between the second electrode 13 and the third electrode 14. As a non-limiting example, due to the high energy charged particles and the front entrance of the irradiation beam, the spacing D = 10
0 μm and X = 3 mm. However, if the volume of the amplification space 15 is small, in the case of FIG. 1, the distance D and the distance between the first electrode 11 and the second electrode 13 may be selected to be very close to the dimension of the gap Fe in the same direction as the gap Fe. it can. Thus, especially when the gas filling the gas chamber is xenon, the interval X can be 1 mm. In such a case, when the irradiation beam is, for example, an X-ray having an energy of 50 keV, the energy of the X-ray fluorescence in the gas is close to 30 keV.
Photoelectrons and secondary electrons of V energy are converted into a conversion space 12
And the conventional detector could not separate photoelectrons and secondary electrons. If two signals appear in the detector, the event is negated as an error. Reducing the spacing D to a value on the order of 1 mm has the effect of greatly reducing the likelihood that X-ray fluorescent photons will be captured, thereby eliminating the appearance of double signals.

Further, according to a particularly remarkable feature of the device of the present invention, the potential applied to the first electrode 11, the second electrode 12, and the third electrode generates a first electric field E1 and a second electric field E2. The electric field is generated by the voltage source V13 so that the electric field is constituted by parallel electric field vectors in the conversion space 12 and the amplification space 13.
And V11 can be selected. These electric fields are perpendicular to the electrodes and have an amplitude ratio ρ = E2 / E1> 10.

In one non-limiting embodiment, the ratio ρ is 50.

Further, the second electrode 13 is formed by a perforated grid, indicating that electrons generated in the conversion space 12 can be sent to the amplification space 15. Taking into account the electric field amplitude value and the amplification distance D, the amplification length D
By utilizing the avalanche phenomenon limited to the above, it is possible to surely multiply these electrons in the amplification space 15.
This is to generate multiplied electrons near the third electrode 14 forming the anode.

It has been found that the third electrode 14 is effectively formed by a plurality of element anodes under the conditions described later.

Finally, a detection circuit 13 is provided, so that the multiplied electrons can be reliably detected and counted. This detection and counting circuit 3 is connected to each element anode forming the anode.

In a preferred embodiment, for gas filling at atmospheric pressure, an electric field E2 is generated in the amplification space 15 with an amplitude of 100 kV / cm, while the electric field E1 generated in the conversion space 12 is 1 kV / cm. Voltage source V1 such that it has an amplitude, so that a ratio ρ = 100 can be obtained.
3, V11 can be selected.

The shape of the detection device 1 shown in FIG.
Dimensions D and X, amplification space 15 and conversion space 12
The value of the field ratio generated between the following steps:
Electrons created in the gas-filled conversion space 12 are shadowed.
It is transferred to the amplification space 15 through the pole 13 where the electric field
These electrons are avalanche due to the very high value of E2.
Phenomenon (of course, this avalanche phenomenon is very small
D), but in the process
Demonstrate the impact. For this reason, the avalanche surface,
The dimension in the direction perpendicular to the direction of the electric field E2 is also very small.
At most a multiplication distance D / 10 for a gain of 1000
It is. In fact, electrons entering the amplification space 15
Is multiplied by the impact of For an amplification gain of 1000 units, 1
000 $ 2 ⁿThen, n = 10, and the mean multiplication factor is
The path λ = D / 10.

Therefore, the dimension of the avalanche surface is about λ, that is, D / 10. Therefore, the actual dimension of the avalanche pattern generated by the multiplication of each electron in the amplification space 15 is at most D / 10 of the free path λ near the electrode 14.
It will be of the order of magnitude. As a result, as will be described later, if an element anode group having an appropriate size is used, a resolution corresponding to this dimension can be achieved.

Further, due to the proximity between the second negative electrode 13 and the third positive electrode 14 due to the small multiplication distance D, the positive ions generated by the avalanche phenomenon and capable of creating space charge at the level of the anode 14 are generated for 100 ns. It has been pointed out that it is absorbed in a very short time on the stage, which results in a high counting rate of more than about 10 ⁶ times / sec / mm ² . The count rate obtained is therefore 100 to 1000 times higher than the value obtained in a chamber with process wiring of a conventional detector.

On the other hand, it has been pointed out that the collection time of positive ions is several tens of μs in a room or the like with a processing wiring of a conventional detection device, and as a result, the counting rate is limited to a value 100 times lower. .

For a more detailed description of the detector 1, see Georges Charpak and the COMMISS included as reference.
ARIAT A L'ENERGIE ATOMIQUE French patent N ゜ 95
It would be helpful to refer to 11928.

As a particularly useful method, as shown in FIG.
The element anode constituting the third electrode forming the anode 14 can be made of the conductive material indicated by reference numeral 140 in FIG. These element conductors have a longitudinal axis of symmetry denoted by YY in the figure. As can be seen, the longitudinal symmetry axis YY of each conductive element 140 points in a direction that concentrates on the ionizing radiation source S, which is the point of emission of the irradiation beam. With such an arrangement,
The parallax error caused by projecting the plane of the irradiation beam onto the plane of the third electrode 14 constituting the anode can be almost eliminated.

In the embodiment shown in FIG.
0 can be composed of conductive strips, for example,
It is formed of a copper microstrip having a width of 80 to 200 μm or a width of several μm.

These strips can be made by microgravure and covered with a conductive film of copper or gold. These are insulating substrates such as sheets made of epoxy glass material or plastic material, for example, KAPTON.
(Manufactured by DuPont) or the like.

As will be described in more detail below, each strip 1
Reference numeral 40 is connected to the detection and counting circuit 3. Anode 1
In terms of the divergence angle ΔΘ of the irradiation beam in the plane of No. 4, each element electrode 140 is separated from the other element electrodes by an angle ΔΘ / (N−1) when there are N electrodes. The element electrodes 140 are thus arranged in a tidy manner within the divergence angle of the irradiation beam.

According to another embodiment shown in FIG. 4, the conductive components forming the element anode 140 are further illustrated in FIG.
It can be made of a plurality of pads distributed along the long axis YY. These conductive element pads each constitute an element anode and have dimensions substantially equal to the amplification distance in a direction perpendicular to the longitudinal symmetry axis YY. In this way, each element anode 140 can be substantially square with one side equal to or smaller than the multiplication distance D, and two successive element anodes can be, for example, in the longitudinal direction YY and perpendicular to the longitudinal direction YY. They are arranged at the same distance D in both directions. FIG. 4 clearly shows that the conductive components forming the element anode 140 are also systematically spaced within the divergence angle of the irradiation beam. Each element anode 140 is, of course, itself interconnected to the detection and counting circuit 3.

The advantages of the above-described configuration of the element anode are in particular: That is, since the avalanche phenomenon develops only beyond the multiplication distance D, it is easy to select the arrangement of these element anodes to obtain the highest accuracy, but in the case of a room with processing wiring, sufficient function is required. Is required to have a minimum distance between wirings of 1 mm.

The detection and counting circuit 3 as further shown in FIG.
Can, of course, effectively have a plurality of fast amplifying devices 30 each connected to the element anode 140 and providing a detection signal for the element anode in question. Finally, the output of each fast amplifying device is interconnected, for example, with a counting and storage circuit 31.

In order to reliably transport the electrons generated in the conversion space, the second electrode 13 forming the cathode is advantageously formed by a thin conductive plate. FIG. 6 shows the conductive plate.
A non-restricted circular hole is drilled as shown in FIG. As shown in the figure, each hole 130i is separated from other holes by a diameter dimension T and a pitch P, and is arranged in a row of holes. The thickness e of the plate is smaller than the hole diameter T. The electric field in the multiplication space is selected to be large enough for electrons to pass through the grid.

The effective pitch P of the row of holes is D / 10 <P <D
/ 3.

Further, the maximum dimension T of each hole 130i corresponds to the diameter in the case of a round hole, the ratio of which is much larger than the plate thickness e exceeding 5, and has a relation of e << T≤P. The grid constituting the second electrode 13 forming the cathode has a thickness e of 2-5.
It can be exemplified as a grid by electrorefining with a pore diameter of about 20 μm and a pitch of 25 μm, for example.

In a particular embodiment, the plate forming the second electrode 13 has a square hole with a thickness of 3 μm and 20 μm, ie, T = 20 μm and arranged at a pitch of 25 μm. To hold the cathode 13 and the anode 14 in terms of mechanical assembly of the second electrode forming the cathode 13 and in order to ensure the mechanical strength of the cathode, especially in the presence of an electrostatic force applied by a bias electric field , Reference numeral 15 in FIG.
Zero electrically insulating spacers must be provided over a wide area of the amplification space 15. The electrically insulating spacer can be made, for example, of a quartz wire whose diameter is equal to the multiplication distance D.

The high-resolution radiation imaging apparatus which is the object of the present invention as described above can perform high-precision analysis required for diagnosis by mammography.

Another embodiment of the high-resolution radiation imaging apparatus according to the present invention will be described in more detail with reference to FIG.

It is clear in the figure that the device according to the invention has a multi-channel structure, denoted by the reference 121, in the conversion space 12 which can capture the irradiation beam and create electrons. In particular, the multi-channel structure 121 has a first electric field E
It is specified to have a plurality of channels extending in one direction. Therefore, ionizing radiation absorbed by the multi-channel structure creates electrons that ionize the gas in the channel. The accelerated electrons are thus emitted in the corresponding channel and are carried via the second cathode 13 to the amplification space 15.

Neutral particles such as γ-rays are very unlikely to be absorbed in the conversion space 12 in the absence of a multi-channel structure. If a multi-channel structure is present in the conversion space 12, much more gamma rays will be absorbed by the Compton effect or photoelectric effect or by the creation of (electron-positron) pairs. Electrons emitted from the surface of the channels have a path limited by the thickness of these channels. They ionize the gas in the tube and emit electrons that enter the amplification space 15 as described below.

As shown in FIG. 8, in a preferred embodiment,
Structure 121 is a microchannel structure having parallel channels denoted by reference numeral 121i and having at least one opening that appears on the flat surface of the structure.

As further shown in FIG. 8, the assembly with this opening has the same pitch P on the flat surface of the microchannel structure as the row of holes 130i on the grid forming the second electrode 13. A row of holes is formed with the same dimension T. In a preferred embodiment, the flat surface of the microchannel structure, in which all the holes of each channel are present, is located near the second electrode 13 forming the cathode and is naturally electrically connected to the second electrode. Thus each channel 12
The openings of the opening row 1i are arranged to face the holes of the grid 130i that form the second electrodes 13.

More specifically, the structure 121 shown in FIG. 8 can be made of glass tubes arranged in parallel. These glass tubes have a thickness on the order of 2 μm and their walls have the reference number 1211i. The height h of the assembly, that is, the height of the glass tube is about 1-2 μm.

This gold coating, denoted by reference numeral 1210a in FIG. 8, can be formed on the surface of the microchannel structure. The diameter of each channel 121i considering the gold coating is between 10-30 μm.

The microchannel structure manufactured as described above can be manufactured such that glass occupies 25% of the volume of a glass tube having a hole having a diameter of 12 μm and a wall having a thickness of 2 μm. In such a structure, the average density is 0.7 g / cm ³ , but when there is no microchannel structure, for example, when a gas such as xenon is indoors under a pressure of 5 bar, 0.03 g / cm ^3. Density.

The introduction of the microchannel structure 121 can thus increase the average density of the material attempting to capture ionizing radiation by a factor of 20 and thus increase the possibility of capture.

In a tube having a wall thickness of 2 μm, the number of photoelectrons or Compton electrons generated by the capture of ionizing radiation is several k.
If they have energies of eV or more, there is a high possibility that they will escape from the glass wall and enter the holes or channels 121i.

According to a particularly advantageous feature of the microchannel structure device shown in FIG. 8, it is possible to create an electric field E3 parallel to the axis of each hole 121i in a substantially elongated manner inside each hole. For this purpose, a conductive coating 1212i having a high specific resistance can be provided on the surface of each channel 121i. This coating comprises gold coatings 1210a, 121
0b, each electrically connecting to electrodes located on the flat surface of the microchannel structure. Electrode 1
A voltage for deflecting electrons in the channel 121i acts on 210a and 1210b. Channel 121i
Each of the electrons invading one of them receives a force in the deflection direction after the penetration due to the presence of the electric field E3 shown in FIG. Each channel 1
The coating 1212i of 21i can be formed of lead foil having a thickness of several tens of angstroms. The electric field E3 can be created by a suitable voltage source V3. The ionized electrons released into the channels of the microchannel structure are Monsieur Georges Charp
The conversion space is used as one of the multistage processing boxes as proposed by AK, and is further multiplied before being transferred to the amplification space 15. More specifically, the microchannel structure can be used to detect soft X-rays, especially for performing crystallographic analysis operations, as shown in FIGS. It is stated that it can be used even if it enters from the front as shown in FIG.

In particular, an embodiment of a specific circuit for performing detection and counting of multiplied electrons generated by using a circuit having an electrostatic induction relationship with the element anode while performing two-way detection. This will be described in more detail below with reference to FIGS.

As shown in FIG. 9 and as described above, the element anode can be constituted by first parallel conductive strips 140i, 140k to 140n connected to the same potential VREF.

In addition, the circuit that couples in an inductive relationship is formed by second conductive strips 141, 142, 143 and subsequent strips, which are vertically and regularly spaced from the first strip. And emits a signal opposite to the signal appearing on the first strip 140k due to electrostatic induction phenomena imparted to the active charge.

Considering the coupling due to the electrostatic induction phenomenon, for example, the electrons collected on the conductive strip 140k are separated from one or more strips 141, 142, 143. . . For those that radiate upward and are located near the electron bombardment on strip 140k, such as strip 142, when these electrons are collected by conductive strip 140k, the variable electrostatic field is immediately extinguished, thereby causing strip 140
On k and 142, a shock point position pulse is generated which is indicated by a positive two-way reference sign X, Y. Positive ions are created on the element anode, strip 140k, and then travel from the element anode, attracting anions on the element anode. However, the electrostatic lines radiated on the second strip 141-143 and subsequent strips will first have a positive sign to identify the type of X, Y pulse, thereby allowing two-way detection.

As a non-limiting example, the first and second conductive strips can be fabricated on a suitably thick substrate of insulating material, but the thickness, width and strip spacing are empirically determined.

As shown in FIG. 10, the second positive electrode 14 can be formed on a printed circuit board made of an electrically insulating material.
0k is arranged.

According to the description of the previous embodiment, the detection and counting circuit 3 further comprises a strip 140 forming an element anode.
Another embodiment includes an electrostatic detection circuit located on
Is shown in Reference numerals 1410 and 142 in the figure
0 and 1430 indicate conductive strips. Each conductive element strip 1410, 1420, 1430 is associated with a respective element anode, which is periodically subdivided into two element strips,
The electrostatic coupling between 0k and them increases or suppresses the action for k rows of element anodes, respectively.

As shown in more detail in FIG. 11, by way of example, the element strip 1410 has two element strips 14.
10a and 1410b, each element anode 14
Electrostatic coupling with 0k increases or decreases the function for the row of strips in question, respectively.

In the circuit shown in FIG. 12, the ratio between the amplitude of the terminal signal transmitted from the terminals of the first element strip 1410a and the terminal of the second element strip 1410b and the final signal can be measured. This ratio represents a row k of elemental anodes, in the vicinity of which ionized electrons generate corresponding electrical pulses.

As shown in FIG. 11, a second strip 1420, which is a conductive strip, is provided, and the first element strip 1420a and the second element strip 1420a have the same periodic pattern of a multiple of a predetermined ratio with respect to the cycle of the first conductive strip 1410. Subdivided into two element strips 1420b.

Further, a third strip 1430 is provided and subdivided into element strips 1430a and 1430b. The split period of the third strip 1430 is a period of a multiple of some different ratio of the first conductive strip.

The circuit shown in FIG. 12 can measure the amplitude of signals transmitted by capacitive coupling at the ends of the first element strip 1410 and the second element strip 1420 and the amplitude ratio of these signals. First and second conductive strips 1410,
1420 is associated with a third conductive strip 1430, if any, which itself is subdivided into two element strips 1430a, 1430b, for each row k of element anodes 140k substantially opposed to the initially emitted ionized electrons. Make a vernier type measuring system. 11, the detection and counting circuit 3 includes a switch control type logic circuit, an amplifier circuit 3140, and an analog-digital conversion circuit 3.
Row k of element anode 140k where 141 and pulse were found
Is considered to include a circuit 3142 that serves as a conversion table for reporting

For a more detailed description of the function of the electrostatic detection system shown in FIGS. 11 and 12, see Monsieur G.
eorges Charpak French patent application N ゜ 2 680 010
Can be referred to.

Finally, similarly, using the set of electrodes 1410 and 1430 constituting the capacitance detecting circuit for one-dimensional search of the element anode 140k, similarly, the second element strips 140 and 141 in the second direction are used. , 142.. And subsequent strips can be fabricated with a capacitance detection circuit for one-dimensional search. This electrode set consists of the element anode 1
As in the case of 40k, the element strips 140, 14
1, 142 and subsequent extensions of the element strip.

As shown in FIGS. 1 and 2 to 12 described above, regarding the use of the apparatus, the gas in the gas chamber is 1%.
Xenon mixed with a coolant such as CO ² or ethane under a pressure between 0 ² pa and 10 ⁶ pa or a gas mixture of 90% argon and 10% methane by volume, if necessary, can be used.

However, in order to cause electron multiplication by the optical avalanche phenomenon in the amplification space 15, the gas in the gas chamber 10 may be a mixed gas of argon and triethylamine.

In the case shown in FIG. 13, the element anode is made of a transparent conductive element so that light generated by the optical avalanche phenomenon can be transmitted.

In the embodiment shown in FIG. 13, the detection and counting circuit 3 comprises, for example, a luminance amplifying device 330b provided with suitable optical components 300a and an integrating system 310 such as a photosensitive film or CCD camera system. CCD
Camera-brightness amplifier assembly 300a, 300b, 31
Reference numerals 0 and 330b transmit or change the wavelength of an optical avalanche phenomenon (280 nm in the visible light range in the case of triethylamine) generated on the electrode surface.

As a non-limiting example, as shown in FIG. 14, light can be transmitted at the wavelength of the optical avalanche phenomenon or can be combined with a surface capable of converting the wavelength of the optical avalanche phenomenon to a wavelength in the visible spectrum. An element anode can be made using a conductive grid that is prepared. As a non-limiting example, conductive wires, i.e., 15 [mu] m diameter gold-plated tungsten wires, can be assembled at a 50 [mu] m x 50 [mu] m pitch at right angles to make the conductive grid shown in FIG. Each transparent 50 .mu.m element area actually acts like an element anode which transmits the optical energy generated by the optical avalanche phenomenon. This grid can also be constituted by a grid similar to the second electrode 13 shown in FIG. The grid can be placed in place of a UV / VIS converter. The grid shown in FIG. 14 is, of course, connected to the reference potential DREF to form an anode composed of a transparent element anode assembly. The gas chamber is closed by a quartz window or a window made of a plastic material.

The advantage of the embodiment shown in FIG. 13 in which the detection of the optical avalanche phenomenon is performed is that the surface of the avalanche is very narrow as compared with the conventional device which similarly detects the optical avalanche phenomenon. The point is that more accurate information on the position and brightness of the avalanche can be obtained.

The discovery by the electric circuit is not performed each time,
This improvement is very important if avalanche discovery is performed by integration of the emitted photons. Such a working method is used when a radiation source S such as a linear accelerator used in radiation therapy emits a very strong burst of X-rays or γ-rays.
It is also particularly important. In such cases, it is necessary to display hundreds of thousands or millions of avalanches at the same time,
This was not possible with conventional electronic devices. Thus, as particle / ionization electron converters, the microchannel structures described above or Nuclear Instruments and Methods, 124 published by AP JEAVONS, G. Charpak; RJSTUBS.
(1975), 491-503, North-Holland Publishing and Co.
Can be used. In this case, an efficiency of 10-50% can be obtained with an imaging accuracy of 0.5 mm-1 mm for 6 MeV γ-rays currently used in radiation therapy. In this manner, a radiograph of the patient can be taken, while the patient can be treated at a much lower radiation dose than during conventional treatment. Thus, the optical detection method is particularly suitable for optical equipment 300
a, means for obtaining high accuracy when the luminance amplifying device 300b, the CCD camera 310, etc. are used. In this application, the illumination beam can be incident from the side by the method shown in FIG. 1 or from the front as shown in FIG.

When the irradiation beam enters from the side, the measurement takes 50 ms each time, that is, it is time to use one frame of the CCD camera, during which one operation of the detecting device is performed.

However, if the detecting device is the conversion space 1
2. Irradiation beam if the full image of the avalanche generated by the flash of gamma rays used in radiation therapy is obtained by a linear accelerator that has a microchannel converter in it and emits pulses or gamma rays for a very short time. Is particularly suitable. In such applications, the optical avalanche has a very small range,
There is no need to perform image processing such as the calculation of the center of mass of each avalanche and the calculation of the optical center of gravity as previously proposed by ieur Georges Charpak, and a good image resolution can be obtained directly. Therefore, according to this working method, the cost of the equipment and the calculation work time can be greatly reduced as compared with the case where the device according to the prior art is used.

In addition to the above-described application to radiography using X-rays or γ-rays, the apparatus of the present invention also exerts a great effect in β-ray radiography under special conditions described later with reference to FIG. As shown in this figure, in this application the source of ionizing radiation consists of an electrophoretic gel, part or preparation, here labeled G, the gel, part or preparation being given radioactivity in a conventional manner. . An electrophoretic gel is a radiation site of β-rays distributed over the entire cross-section of the gel, part or preparation, and the irradiation beam is composed of a plurality of β-rays sporadically radiated from these various radiation points. The gel G is arranged near the window Fe for the front entrance of the irradiation beam. The support plate SUP indicated by a dotted line or a broken line in FIG. 15 can position a gel, a component, or an adjustment product for observation if necessary.

According to a particular feature of the detection device of the present invention, the first electrode 11 and the second electrode 13 are located close to or less than the distance D separating the second electrode 13 from the third electrode 14. ing. Conversion space 12 and amplification space 1
5 has substantially the same dimensions in a direction perpendicular to the electrodes 11, 13, and 14.

As a non-limiting example, the interval D = 100 μ
m and the interval X are the same, X = 100 μm, and the total thickness of the detection device 1 is 0.2 mm.

Under these conditions, as shown in FIG. 15, the maximum path of the β-ray radiated from any radiation point of the gel G is about the size of the distance X between the first electrode 11 and the second electrode 13. Having. Since electrons are generated on the path of β-rays in the conversion space 12, the positioning accuracy of the corresponding radiation point is better than the value of the distance X. In accordance with the detection device that is the subject of the present invention, a device having a chamber with a parallel surface that positions the emission point of β-rays using a variable gain based on the depth of ionized electrons in the z coordinate direction, Devices that are simpler than current devices can be developed.

A more detailed description of a high-resolution radiation imaging apparatus that enables three-dimensional image analysis with a single exposure using X or gamma-ionizing radiation will be described with reference to FIGS.

Based on FIG. 16, it is considered that the radiation source S emits ionizing radiation having a predetermined solid angle ΔΩ and extending.

According to the embodiment shown in FIG. 16, the radiation imaging apparatus of the present invention has a collimator CO, and the collimator CO has a long axis gap having reference numerals F1... Fi. As shown in the figure, there are a plurality of long axis gaps forming a plurality of diaphragms through which a plurality of flat irradiation beams can actually pass. Each flat illumination beam is approximately distributed in a plane containing one of the long axis gaps and the source S in the gap assembly. As shown in FIG. 16, the planes containing one of the flat illumination beams together form a bundle of planes that converge toward the source of ionizing radiation.

As also shown in the figure, the apparatus of the present invention has a module for detecting a set of flat irradiation beams,
This makes it possible to illuminate the inspection object SU placed downstream of the collimator CO. The detection module comprises a device for detecting ionized particles as previously described with reference to FIGS. 1 to 14, wherein the detection device 1 is arranged facing a corresponding flat illumination beam. In this way, each detection device with reference numerals 11, 1i-1n corresponds to a gap F1, Fi-Fn. Further, in particular, windows Fe1 of the respective detection devices, which are entrances of the flat irradiation beam,
The Fei-Fen is disposed on a plane formed by a gap Fi through which the ionizing radiation source S and the present apparatus pass the associated flat irradiation beam. The window Fei can be formed in a normal collimator CO 'as shown in FIG.

In FIG. 16 and FIG.
It can be seen that -1n is symmetrically inclined with respect to the center detector having the reference number 1i.

In order to ensure the independence of each detection device 1i,
These detectors are provided with a shield made of a sheet of lead or tungsten, referenced 11i, to ensure the independence of each detector against ionizing radiation radiated by adjacent plate-like irradiation beams. it can.

The high-resolution radiation imaging apparatus which exhibits particularly excellent performance as long as the used detector 1 has a very small thickness has been described. In fact, taking into account the conversion space 12 and the amplification space 15, the total thickness is 1.
It is on the order of 1 mm. In particular, due to the special advantages of the high-resolution radiation imaging device, which is the subject of the present invention, it is possible to use a device comprising a number of detection devices as shown in FIGS. These detectors operate as if in parallel,
The increase in the number of the detection devices can reduce the scanning time of the inspection object SU in accordance with the ratio n if n detection devices are used.

It is obvious that all the n detectors can be arranged in one pressurized gas chamber with a lead separation wall provided. Here, the separation wall 11i is as described above, and is for preventing secondary radiation generated in the detection device from hindering detection in the adjacent detection device.

Finally, if the ionizing radiation has a high energy exceeding 1 MeV and is a high-energy radiation such as a gamma ray suitable for industrial radiography, the detector 1 used is replaced with the microchannel structure 12. In addition, a plurality of thin sloping sheets, such as the previously described tantalum sheets arranged at an angle of incidence of about 1 °, may be provided according to conventional and known techniques with respect to the average direction of the ionizing particle illumination flux. These sheets can ensure the conversion of the particles.

This embodiment makes it possible, on the one hand, to increase the possibility of capturing ionized particles and of the generated photoelectrons in accordance with the prior art, on the other hand, on the other hand, to the detection device 1 according to the invention.
Due to the use of the very high counting rate capability of the present invention, the operating costs of the particle accelerator generating the ionized particles used can be greatly reduced.

[0107]

Since the present invention is configured as described above, the resolution of image formation can be increased, and the radiation dose applied to the inspection object can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a high-resolution radiation imaging apparatus to which the present invention is applied.

FIG. 2 is a longitudinal sectional view of a high-resolution radiation imaging apparatus to which the present invention is applied.

FIG. 3 is a cross-sectional view taken along the line AA in FIG. 1 of the first embodiment of the high-resolution radiation imaging apparatus to which the present invention is applied;

FIG. 4 is a cross-sectional view taken along the line AA in FIG. 1 of a second embodiment of the high-resolution radiation imaging apparatus to which the present invention is applied;

FIG. 5 is a diagram showing details of an embodiment of a specific detection circuit used by the high-resolution radiation imaging apparatus of the present invention.

FIG. 6 shows a detail of an advantageous embodiment of the grid forming the cathode of the detection device in accordance with the subject of the present invention.

FIG. 7 shows an advantageous embodiment of the high-resolution radiation imaging device according to the invention, in which the multi-channel structure is arranged in the ionizing radiation conversion space of the detection device used by the device and the multi-channel structure; It is a figure which shows the detailed Example of.

FIG. 8 shows an advantageous embodiment of the high-resolution radiation imaging device of the present invention, wherein the multi-channel structure is located in the ionizing radiation conversion space of the detection device used by the device and the multi-channel structure. It is a figure which shows the detailed Example of.

FIG. 9 shows a different embodiment of the high-resolution radiation imaging device which is the subject of the present invention, wherein a capacitive coupling circuit is used to reliably detect the electrons generated by ionizing radiation.

FIG. 10 shows a different embodiment of the high-resolution radiation imaging apparatus which is the subject of the present invention, wherein a capacitive coupling circuit is used to reliably detect the electrons generated by ionizing radiation.

FIG. 11 shows a different embodiment of the high-resolution radiation imaging apparatus which is the subject of the present invention, wherein a capacitive coupling circuit is used to reliably detect the electrons generated by ionizing radiation.

FIG. 12 shows a different embodiment of the high-resolution radiation imaging apparatus which is the subject of the present invention, wherein a capacitive coupling circuit is used to reliably detect the electrons generated by ionizing radiation.

FIG. 13 shows another embodiment of the high-resolution radiation imaging apparatus which is an object of the present invention, and detects electrons generated by ionizing radiation by causing an optical avalanche phenomenon.

FIG. 14 shows another embodiment of the high-resolution radiation imaging apparatus which is the subject of the present invention, and detects an electron generated by ionizing radiation by causing an optical avalanche phenomenon.

FIG. 15 is a diagram showing a high-resolution radiation imaging apparatus which is an object of the present invention using β-ray imaging.

FIG. 16 shows a high-resolution radiation imaging apparatus which is the subject of the present invention, in which a three-dimensional analysis of an inspection object given a radiation beam having a predetermined solid angle is possible. , A plurality of single detection elements are arranged in an overlapping manner.

FIG. 17 shows a high-resolution radiation imaging apparatus which is the subject of the present invention, in which a three-dimensional analysis of an inspection object given a radiation beam having a predetermined solid angle is possible. , A plurality of single detection elements are arranged in an overlapping manner.

[Explanation of symbols]

 Reference Signs List 1 detection device 2 bias circuit 3 counting circuit 10 gas chamber 11 first electrode 12 conversion space 13 second electrode (cathode) 14 third electrode (anode) 15 amplification space 30 amplification device 31 storage circuit 121 multi-channel structure 130i hole (grid) 140) Conductive material (strip, element electrode) 150 Electrically insulating spacer F Long axis gap S Source B Frame SU Inspection object Fe Entrance window VREF Reference voltage D interval E1 First electric field E2 Second electric field E1 First electric field V11, V13 voltage source

Claims (15)

[Claims] 1. A high-resolution radiation imaging apparatus using ionizing radiation, comprising: an ionizing radiation source that emits ionizing radiation diverging from the apparatus; and a flat irradiation beam in a plane substantially including the flat irradiation beam. Having a gap between the long axes forming a stop suitable for emitting a beam, and a detecting device for detecting a light beam carried through the inspection object irradiated with the flat irradiation beam, wherein at least one of the detecting devices is provided. The ionized particle detector includes at least one gas chamber having an entrance window of the irradiation beam, and the first, second, and third plate electrodes included in the gas chamber. When included, the electrodes are arranged parallel to each other to form a space for converting the irradiation beam into electrons and a space for amplifying these electrons by multiplication, and the entrance window is provided with the irradiation window. The amplification space has a multiplication length of less than 200 μm at a distance separating the second and third electrodes, and is arranged flush with the conversion space to ensure that the beam enters the conversion space. The detection device further raises the first electrode to a first potential, raises the second electrode to a second potential higher than the first potential, and raises the third electrode to the A bias circuit suitable for raising the potential to a third potential higher than the second potential, wherein the second electrode is perforated to form a cathode, and directs electrons generated in the conversion space to an amplification space. The third electrode forms an anode composed of a plurality of insulated element anodes, and the potential applied to the first, second and third electrodes is within the conversion space and the amplification space. A first electric field and a second electric field substantially parallel thereto And each of these electric fields has an amplitude ratio that is approximately perpendicular to each of said electrodes and greater than 10, thereby generating multiplied electrons in the vicinity of said third electrode forming an anode, within the amplification space. It is possible to multiply these electrons by an avalanche phenomenon limited to the amplification length, and comprises a device for detecting and measuring the multiplied electrons coupled to the element anode forming the anode. High-resolution radiation imaging device. 2. The method according to claim 1, wherein the entrance window is arranged in a lateral direction on the gas chamber so that the irradiation beam can be incident parallel to the electrode, or the irradiation window is incident on the electrode from the front. 2. The device according to claim 1, wherein the inlet window is located on the gas chamber surface facing the second electrode forming the cathode. 3. The element anode is formed by conductive elements having a longitudinal axis of symmetry, such that the longitudinal axis of symmetry of each conductive element is concentrated toward an ionizing radiation source that forms the emission source of the irradiation beam. 2. The apparatus according to claim 1, wherein the parallax error caused by the projection of the plane of the irradiation beam onto the third electrode surface forming the anode can be substantially eliminated. 4. The conductive element forming the element anode has a length substantially equal to the amplification distance in a direction perpendicular to the longitudinal symmetry axis direction, and two consecutive along the same vertical direction. 3. Apparatus according to claim 2, wherein the conductive elements are regularly spaced within the divergence angle of the irradiation beam. 5. A plurality of fast amplifying devices, said plurality of fast amplifying devices including one fast amplifying device coupled to a conductive element forming an element anode and transmitting an electrical detection signal to said element anode. 2. The device according to claim 1, further comprising a counting and storage device connected to the output of the device. 6. The second electrode is formed by a conductive grid, the grid having an ordered array of holes with a pitch P, wherein the hole pitch is D in the plane of the second electrode.
2. The device according to claim 1, wherein the maximum dimension T of the holes is greater than the grid thickness e and less than P, between / 10 and D / 3. 7. A multi-channel structure capable of capturing an irradiation beam and creating electrons in the conversion space,
The apparatus of claim 1, wherein each channel of the multi-channel structure extends in a direction of the first electric field. 8. The microchannel structure, wherein the multichannel structure is formed of a block of material that absorbs the ionizing radiation of the irradiation beam, wherein the microchannel structure has at least one opening open in the plane of the structure. Comprising microchannels, said aperture assemblies forming on said flat surface an array of holes of the same pitch P and of the same dimension T as the array of holes in the grid forming said second electrode; The row of openings is arranged near the second electrode forming the cathode, the openings of the opening row are placed facing the holes of the grid forming the second electrode, 8. The device according to claim 7, wherein the holes are thus facing. 9. The detection and counting device further includes an electrostatic detection circuit configured by capacitive coupling with each element anode, wherein the electrostatic detection circuit includes at least a first conductive strip, The active strip is periodically divided into two element strips, and the electrostatic coupling between each element strip and each element anode increases or suppresses its function for each of the k rows of element anodes to which each element strip is connected. The apparatus according to claim 1, wherein the apparatus has a function of performing. 10. The gas contained in the gas chamber is 10 ²
2. The apparatus according to claim 1, wherein the xenon is mixed with a quench material under a pressure between pa and 10 ⁶ pa. 11. The gas contained in the gas chamber is made of a mixture of argon and trimethylamine so as to cause electron multiplication in the amplification space by an optical avalanche phenomenon, and the element anode is made of a transparent conductive material. The device according to claim 1, wherein the device transmits light generated by an optical avalanche generated by the active element. 12. The element anode is formed of a conductive grid associated with a surface that transmits light at an optical avalanche wavelength or converts the optical avalanche wavelength to a wavelength in the visible spectrum. The apparatus according to claim 11, wherein 13. The apparatus according to claim 13, wherein the counting device is constituted by integrating means such as a photosensitive film, and is associated with light and luminance amplifying means.
13. The device according to claim 12, wherein the device is placed on a surface and is capable of transmitting or changing the wavelength of the optical avalanche phenomenon. 14. A high-resolution radiation imaging apparatus using ionizing radiation, the source comprising an ionizing radiation source for emitting divergent ionizing radiation, the apparatus comprising: a plurality of apertures adapted to emit a plurality of planar illumination beams. Including a collimator including a plurality of long axis gaps forming
Each of the plurality of flat irradiation beams is substantially located in a plane including one of the gaps of the plurality of long axes, and the plane including one of the flat irradiation beams is combined with the ionizing radiation source. Forming a bundle of planar light beams converging toward each other, comprising a device for detecting a set of planar illumination beams, wherein said detection device comprises at least one ionized particle detection device, wherein said ionized particle detection device comprises at least an entrance of said irradiation beam. When including one gas chamber having a window and first, second, and third plate electrodes included in the gas chamber, each of the electrodes multiplies a space for converting an irradiation beam into an electron, The entrance window is arranged flush with the conversion space so as to ensure that the irradiation beam enters the conversion space; The space is the distance separating the second and third electrodes, and has a multiplication length of less than 200 μm, the detection device further raises the first electrode to a first potential, A bias circuit suitable for raising the second electrode to a second potential higher than the first potential, and raising the third electrode to a third potential higher than the second potential, The second electrode is perforated to form a cathode, and the electrons generated in the conversion space can be sent to the amplification space,
The third electrode forms an anode composed of a plurality of insulated element anodes, and the potential applied to the first, second, and third electrodes is the first and second in the conversion space and the amplification space. Generating a second electric field that is substantially parallel to each other, and each of these electric fields has an amplitude ratio of more than 10 that is substantially perpendicular to each of the electrodes, thereby being multiplied near the third electrode forming the anode. It is possible to multiply these electrons by an avalanche phenomenon limited to the amplification length in the amplification space to generate electrons, and the multiplied electrons coupled to the element anode forming the anode are detected. A device for measuring, wherein the at least one ionized particle detection device is placed facing each plate-like irradiation beam, and each detection device emits an ionizing radiation source and a plate-like irradiation beam associated with this detection device. High resolution radiographic imaging apparatus being located in the plane formed by the exit to the gap. 15. For imaging using β-radiography, there is an ionizing radiation source consisting of an electrophoretic gel or a radioactive site located near the window for the front entrance of the irradiation beam at the β-ray emitting site. And wherein the first and second electrodes are separated by a distance X that is closer to or less than the distance between the second and third electrodes, and the conversion space and the amplification space are perpendicular to the electrodes. Direction, which limits the length of the path of each beta ray emitted from the ionizing radiation source to a value approximately equal to the distance X between the first and second electrodes; 2. The apparatus according to claim 1, wherein the positioning accuracy of the radiation point can be set to a value close to or smaller than the distance X.